The present invention relates to a method for loading green tires in a laterally aligned two chamber type tire curing press.
In FIG. 1 is shown one example of a green tire loading device in the prior art provided in a tire curing press A.
A green tire loading apparatus in the case of carrying out loading of green tires by making use of a combination of vertical movement and horizontal swinging motion of the green tires upon loading the green tires in the so-called two-chamber type tire curing press A in which two sets of metal tire molds are provided in one tire curing press so that two green tires can be simultaneously cured, comprises green tire loading devices B.sub.1 and B.sub.2 respectively on the opposite sides of the tire curing press.
The separate and individual provision of loading devices on the left and right sides as described above results in the following facts:
(1) There is a shortcoming that vertical drive sources and swing drive sources for the green tire loading devices B.sub.1 and B.sub.2 are provided separately and individually on the left and right sides and hence the installation cost is high.
(2) The green tire loading apparatus is necessitated not only to hold "green tires to be cured next" and stand by during the period when green tires are being cured in the tire curing press, but also to store "green tires to be cured next to the next" on tire placing tables during that period. In order to achieve this storage, the following two types were employed in the prior art.
The first type is the type in which green tire placing tables are fixedly disposed at positions II in front of the green tire curing press and green tires are stored on these green tire placing tables. In this case, the "green tires to be cured next" are gripped and suspended at green tire loading positions which are at an upper level at the positions II, and while these green tires are held at the upper level, the "green tires to be cured next to the next" are placed on green tire placing tables at a lower level at the positions II.
However, in the case of this type, since a sufficient vertical gap space for facilitating the placing work of a green tire is necessitated between the already gripped and suspended green tire and the green tire placing table, it is necessary to hold the already gripped green tire sufficiently high with respect to the green tire placing table.
On the other hand, in a curing press making use of only vertical movement which is recently believed favorable as a high precision tire curing press, since contrivance has been made to minimize the vertical stroke of the press for the purpose of improving productivity and maintaining a high precision for a long period, a vertical stroke of a green tire loading device is also made small, hence if the stroke necessitated for loading a green tire into the curing press is kept intact, then the sufficient vertical gap space for placing the "green tire to be cured next to the next" as described above cannot be reserved between the gripped and suspended "green tire to be cured next" on the green tire placing table, and therefore, it becomes necessary to give a surplus stroke to the green tire loading device for the aforementioned preparatory work and carry out complex vertical operations of the green tire loading device such that the loading device is raised up to a higher position for the purpose of the preparatory work, and after completion of the preparatory work the loading device is lowered to a lower position adapted for loading and is made to stand by.
In addition, since a curing press is constructed so as to be able to cure various sizes of green tires, the tire metal molds are replaced in accordance with the size of the tires to be produced. However, as the aforementioned green tire placing tables are disposed in front of the press, the green tire placing tables would hinder the replacement operation and hence the green tire placing table is either removable or is of such a type that it can be swung to another position not hindering the operation only during the replacement operation.
Accordingly, the above-mentioned type of method for loading and storing green tires cannot be said to be suitable for a curing press which can achieve only vertical movement.
The second type is the type in which green tire placing tables are swingable forth and back between the positions II and the positions III shown in FIG. 1 for the purpose of eliminating the shortcomings of the above-described first type which are that:
(a) A large stroke is necessitated for the vertical movement of the green tire loading device. PA1 (b) Control for the vertical movement of the green tire loading device is complex. PA1 (c) Upon replacement of metal molds, there occurs a necessity for displacing the green tire placing tables to positions not hindering the displacement, through a special operation. PA1 (1) Vertical reciprocating motion of at least the green tire loading devices for the respective left and right chambers is carried out by making use of the same vertical reciprocating track and the same vertical reciprocating driving devices for each and thereby a lowering of the installation cost is achieved. PA1 (2) Swinging motion of the green tire placing tables is carried out by making use of a simple driving device for the left and right ones, and thereby a further lowering of the installation cost is achieved. PA1 (3) A curing press having a smaller overall width than the necessary space width for the curing press of the heretofore known type is formed, thus an installation space for the curing press and providing an economical curing press. PA1 (4) A tire curing press favorable for a automatic green tire delivery and setting apparatus is formed. More particularly, when green tires are set on green tire placing tables by means of a green tire automatic delivery and setting apparatus, only one stop position in front of the press of the aforementioned automatic delivery and setting apparatus suffices for the desired operation. PA1 (5) An improved green tire loading device is provided, in which inversion of tire by inverting a green the device is not employed but a green tire is inverted on a green tire holding and supplying device so that the green tire may be automatically set on upwardly directed claws of a green tire loading device, whereby movement of a green tire loading device is reduced to enhance precision, and also the labor of an operator is reduced, and furthermore a green tire loading device which is favorable for carrying out automatic setting of a green tire supplied from a green tire automatic delivery car, is provided.
In the case of the second type, indeed the aforementioned shortcomings (a), (b) and (c) can be eliminated, but this type also has a shortcoming that it becomes necessary to drive the left and right green tire placing tables to swing, so that it is difficult to use the same drive source for both the left and right green tire placing tables, and hence an installation cost becomes high.
(3) Furthermore, if the preparatory work for green tires is carried out at the positions III, as will be appreciated from FIG. 1, a wide space for the curing press becomes necessary, and so, there occurs a disadvantage that in the case of linearly aligning ten and more curing presses in one line (as is quite generally practiced), a long space is necessitated.
(4) Moreover, since a curing press is perfectly automated from the loading of green tires up to the delivery of completed tires provided that green tires have been supplied onto the green tire placing tables, research and investigation for automatic supply and setting of green tires onto the green tire placing tables is being conducted. However, if the green tire placing tables are provided at the left and right end portions of a press as separated from each other as described above, such arrangement is not suitable for automatic setting of green tires supplied from an automatic supply apparatus. More particularly, in order for an automatic supply apparatus to stop at one position in front of the press and set green tires onto the respective green tire placing tables, the stop position must be sufficiently close to the respective green tire placing tables, but with the above-described loading apparatus, the stop position would be too far from the respective green tire placing tables, and as a result, it becomes necessary that the automatic supply apparatus should stop at the respective positions in front of each of the green tire placing tables, and because of such reasons, disadvantages would arise such as stopping of the apparatus twice for each press, complexity of control and loss of time.
On the other hand, the heretofore practiced method for loading a green tire into a curing press is the so-called "lower-bead-set-first" system in which a lower bead portion of a green tire is at first made to seat on a lower bead ring of a lower metal mold section. According to this method, as shown in FIG. 2, the green tire supported by a bladder expanded at an extremely low pressure is unstable, moreover even a quite small unevenness of the bladder would result in tilting of the green tire with respect to a center axis, and hence when it is tried to make an upper bead portion of the green tire to seat on an upper bead ring while bringing the upper bead ring close to the green tire, miss-seating would sometimes arise.
In order to obviate this shortcoming, it is desirable to carry out shaping of a green tire by making a bladder inflate within a green tire with its upper bead portion seated on an upper bead ring of an upper mold section and with its lower bead portion supported by a lower bead ring of a lower mold section as shown in FIG. 3. However, even if it is tried to carry out the shaping work illustrated in FIG. 3 by making the lower bead portion of the green tire seat on the lower bead ring while suspendingly gripping the upper bead portion of the green tire by means of a green tire loading device used in the prior art and, after the suspending grip by the aforementioned loading device has been released, by bringing the upper bead ring close to the green tire and making the upper bead of the green tire seat on the upper bead ring, the shaping work would fail.
More particularly, as soon as the suspending grip by the aforementioned loading device is released, the green tire would buckle as shown in FIG. 4.
In order to eliminate the above-mentioned shortcoming, the inventor of this invention has recently proposed a novel method disclosed in his U.S. Pat. No. 4,452,577, in which green tire grip claws of a green tire loading device are formed in an upwardly directed form (those used in the prior art were directed downwardly) so as to grip a lower bead portion of a green tire (in the prior art an upper bead portion was gripped), the respective ones of the aforementioned grip claws are associated with movable support claws for supporting a tread portion of a green tire from below, and thus a lower bead portion of a green tire is gripped and simultaneously its tread portion is supported from below at a position outside of a tire curing press. Under this condition the green tire is loaded into the press, the upper bead portion of the green tire is made to seat on an upper bead ring of an upper metal mold section, the seated bead portion of the green tire is suspendingly gripped by an upper bead gripping device of the upper metal mold section, and after the green tire has been lowered to make the lower bead portion of the green tire seat on the lower bead ring of the lower metal mold section, a bladder is inflated within the green tire as shown in FIG. 3.
According to this method, since the green tire is suspended at the portions above the center of gravity, it is also advantageous when the lower bead ring is made to enter into the lower bead of the green tire. However, when the green tire loading device receives a green tire at a position outside of the press, an operator must carry up the heavy tire to set it at the upwardly directed grip claws of the green tire loading device, and in the case where the weight of the green tire is approximately as heavy as 100 kg as is the case with a radial tire for use in trucks and buses, it becomes difficult for the operator to manually set the green tire with operator's hands. Nevertheless, if a modification is made such that a green tire on a green tire automatic delivery car is directly placed on the upwardly directed claws by means of an automatic setting device equipped on the automatic delivery car, then the number of green tires which can be preliminarily prepared for the next curing operation during the period when curing is being carried out in the curing press becomes two (in the case of a two-chamber type curing press), and hence a margin of only one cycle is maintained, so that in the event that a plurality of presses are installed, the aforementioned green tire automatic delivery and automatic setting apparatus must to move around busily, and therefore, the number of presses which can be dealt with by means of one automatic delivery and setting apparatus as described above would be limited.
Therefore, the inventor of this invention proposed and disclosed in copending laid open No. 54-9039 Japanese patent application and U.S. Pat. No. 4,452,577 a method which makes it possible to prepare four green tires in front of a press by gripping an upper bead portion of a green tire placed on a green tire placing table with a green tire loading device, thereafter raising the green tire loading device up to an appropriate height, inverting the green tire loading device so as to make the green tire upside-down on the green tire loading device, and then loading the green tire into the press.
However, the proposed green tire loading device necessitates vertical movement, swinging movement for loading and further inverting movement, and hence it has a shortcoming that since the structure becomes complex and includes many movable portions, it is difficult to produce so as to operate with high precision.